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Southern Cross Medical Library

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Complex regional pain syndrome (CRPS)

Complex regional pain syndrome (CRPS) is a long-term disorder of the nervous system. It is a collection of signs and symptoms typically at the site of an injury to an arm or leg.  Those symptoms may include burning type pain, changes in skin and bone tissue, excessive sweating (hyperhidrosis), swelling of an extremity, and extreme sensitivity to touch.
CRPS is poorly understood and difficult to diagnose.  Better treatment outcomes are more likely if started during the first three months of the condition. 
Although it can start at any age it is most common between the ages of 40 and 60 years. CRPS occurs more frequently with women than men.
CRPS was first recorded in the 19th century during the American Civil War. Doctors noted veterans were experiencing pain after their wounds had healed. CRPS may also be referred to as reflex sympathetic dystrophy syndrome (RSDS), sympathetic dystrophy syndrome (RSD), causalgia, the shoulder-hand syndrome and Sudeck’s atrophy.


The exact cause of CRPS is unknown but may result from irritated and damaged nerves of the sympathetic nervous system. Even relatively minor trauma to a body part may lead to CRPS.
The sympathetic nervous system is a division of the autonomic nervous system (ANS) which controls unconscious bodily functions including digestion, regular beating of the heart, blood flow, sweating and salivation.  In CRPS dysfunctional sympathetic nerves are thought to send inappropriate messages to the brain. These interfere with normal messages regarding sensation, temperature and blood flow.

A number of different events can trigger the condition. These include:

CRPS also occurs in some people with fibromyalgia.  A common nerve entrapment condition that can trigger CRPS is carpal tunnel syndrome.  In approximately one third of all cases, no trigger can be identified.

Signs and symptoms

CRPS can affect the nerves, skin, muscles, blood vessels and bones simultaneously. Symptoms can be gradual or rapid in onset and can vary in severity. They normally occur in three stages: acute, dystrophic and atrophic.  Signs and symptoms occurring in these three stages may include:

Acute phase (1-3 months)

  • Burning pain
  • Swelling of an extremity
  • Vasospasm (constriction of blood vessels) affecting skin colour and temperature. 
  • Excessive sweating
  • Tenderness

Dystrophic (3 to 9 months)

  • Intensified pain
  • Shiny skin
  • Thickened skin
  • Contracture development (tightening and shortening of muscles)
  • Diminished swelling

Atrophic (9 months or longer)

  • Skin changes become irreversible
  • Significant osteoporosis can be shown on x-ray
  • Thinning of the fatty layers under the skin
  • Restricted movement due to contractures
  • Pain unyielding and may have spread to other areas of body


CRPS is poorly understood and often misdiagnosed. Diagnosis is usually made based on pain symptoms and clinical signs.  A doctor will usually make a diagnosis of CRPS based on the following: 

  • A full medical history
  • Discussion of current pain symptoms
  • X-rays and magnetic resonance imaging (MRI) scans to assess bone changes
  • Blood tests to rule out other causes


Treatment is generally most effective in the first three months of the condition. If left untreated the disorder can spread to other areas of the body. The usual pattern of spread is up the affected extremity and on to the same side of the body. It may also spread to the opposite side of the body. Specialist intervention early on is the key to a successful outcome.
A doctor may need to try a variety of treatments. Least invasive is the application of cold or heat. Most invasive is chemical or surgical sympathectomy (removal of affected sympathetic nerves). Surgical sympathectomy involves cutting the nerves and while this can stop pain almost immediately other sensations may be destroyed as well.

Other treatments include: 

  • Sympathetic block (injection of a local anaesthetic into affected sympathetic nerves to block pain)
  • The use of low dose tricyclic antidepressants and anticonvulsants to relieve pain sensitivity
  • Medications including analgesics (pain relievers), vasodilators (increase diameter of blood vessels) and corticosteroids (reduce inflammation)
  • Desensitisation of the affected area using techniques such as TENS (transcutaneous electrical nerve stimulation), massage and brushing of the skin
  • Implantation of spinal cord stimulation devices and pain medication-releasing pumps into the spinal canal
  • Physiotherapy (exercising affected limb to prevent contractures, maintain muscle strength and movement, and build aerobic fitness)
  • Psychological counselling and education regarding the condition
  • Regular aerobic exercise eg: swimming / brisk walking


Recovery is variable in CRPS. The prognosis is better with early treatment. Approximately 50 per cent of patients with CRPS suffer pain for longer than six months. Some patients with severe symptoms may not respond to treatment. For these individuals a pain management programme aimed specifically at chronic pain can be beneficial. This is usually done through a hospital-based multidisciplinary pain clinic involving medical practitioners, physiotherapist, occupational therapists, psychologists and other health professionals.  

Support and information

For further information or support, contact your GP or practice nurse.
Community support groups that may be able to assist include:
Pain Action in New Zealand Inc. (PAINZ)
PO Box 32 074
Christchurch 8011
Ph: (03) 366 0716  

References (2011) Complex regional pain syndrome.  Leawood, KS: AmericanAcademy of Family Physicians -
MayoClinic (2011) Comples regional pain syndrome. Rochester, MN: Mayo Foundation for Medical Education and Research.
Shiel Jr, W.D. (2011). Relfex sympathetic dystrophy (RDS. Complex regional pain syndrome, CRPS). New York: WebMD LLC.
National Institute of Neurological Disorders and Stroke (2013) NINDS complex regional pain syndrome information page. Bethesda: National Institutes of Health
Last Reviewed - June 2013 


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